The economic impact of infectious diseases in food animal production is well appreciated. Infectious diseases reduce profits, increase production costs, and endanger the overall wholesomeness of the food products, as well as effect the performance, health and welfare of the animal. This disease status can reduce the yield and quality of milk resulting in great economic loss to the dairymen. In some cases, infectious microbial diseases can cause morbidity and mortality of newborn, young (e.g., replacement stock) or adult animals.
The agricultural industry presently relies on antibiotic therapy and vaccines to decrease losses caused by clinical and subclinical infectious diseases, including gastrointestinal disease, respiratory disease, and systemic disease. However, for some conditions, antibiotics are ineffective, may prolong the condition, or induce a carrier state. Vaccines have often proven to be an effective means of controlling infectious diseases, but, concerns relating to adverse effects or lack of protection against multiple microbes have been a major drawback to current vaccines. For instance, vaccines are available that contain one or more immunogens against an individual genus, species, or strain of microbe; however, few, if any, provide cross-protection or stimulate broad-based immunity against multiple strains, species or genera of microbe.
Vaccines containing molecules obtained from gram negative microbes typically include contaminating levels of lipopolysaccharide (LPS), a component of the outer membrane of most gram negative microbes. The presence of LPS in an injectable product can result in an inflammatory response at the site of injection that can result in swelling, tenderness and often the formation of a granuloma at the site of injection. In rare cases, it can result in anaphylactic shock and death. This non-specific inflammatory response in a production animal can result in significant economic losses due to increasing the likelihood of disease by increasing the level of stress of the animal, and negatively effecting performance characteristics of the animal. In addition, the formation of a granuloma at the injection site can result in significant economic losses due to blemishes and scarring of the carcass which are often trimmed during processing resulting in the loss of product and down grading of the carcass. While methods for removal of LPS from compositions exist, this is often not feasible for use with vaccines that include whole cells. Moreover, due to the high costs of removing LPS from solutions, it is typically not economically practical to remove LPS from vaccines for use in non-human animals.